The present invention concerns ion beam implanters and more particularly to ion beam implanters having a lens through which ions that make up an ion beam pass to produce a controlled angle of impact between ions and a work-piece.
Axcelis Technologies, assignee of the present invention, sells products for treatment of silicon wafers during Integrated Circuit fabrication. One such product or tool creates an ion beam that modifies the physical properties of wafers that are placed into the ion beam. This process can be used, for example, to dope the silicon from which the untreated wafer is made to produce a semiconductor material. Controlled use of masking with resist materials prior to ion implantation as well as layering of different dopant patterns within the wafer produce an integrated circuit for use in one of a myriad of applications.
Prior art U.S. Pat. No. 5,177,366 to King et al and U.S. Pat. No. 5,091,655 to Dykstra et al. discuss methods of using two pair of electrostatic scanning electrodes to generate parallel ion beams. The ""366 patent concerns an ion beam implantation system wherein an ion beam is controllably deflected from an initial trajectory as it passes through spaced parallel plates that are biased by a control circuit. Once deflected, the ion beam passes through electrodes positioned along a beam travel path that both re-deflect the once deflected ion beam and accelerate the ions to a desired final energy. Ions within the beam exit the accelerator and impact a work-piece at a uniform, controlled impact angle due to ion focusing in a scanning plane and an orthogonal cross plane.
The ""655 patent relates to an ion beam that is controllably deflected from an initial trajectory as it passes through spaced parallel plates that are biased by a control circuit. Once deflected, the ion beam enters an accelerator that both re-deflects the once deflected ion beam and accelerates the ions to a desired final energy. When the beam exits the accelerator it moves along a trajectory that impacts a work-piece. Ions making up the ion beam all impact the work-piece at a uniform, controlled impact angle.
A printed publication entitled xe2x80x9cThe Nissin NH-20SP medium-current ion implanterxe2x80x9d to Nagai et al describes a medium current ion implanter. The implanter has a pair of so-called kickback electrodes H2 that compensate for side to side scanning introduced by an initial set of electrodes; The sweep-voltage waveform applied to the H1 and H2 electrodes is generated by a digital-waveform generator, or a waveform controller.
An ion implanter includes an ion source for emitting ions generated from a source material and structure for causing ions to exit the source. A scanning electrode scans ions from side to side in a controlled manner to form an ion beam having a width. A lens structure defines a region into which the ions pass to deflect ions away from an initial trajectory downstream from the scanning electrode as they enter the lens structure.
The lens structure includes first and second electrodes spaced apart along a direction of ion movement which extends on opposite sides of a beam path across a width of the ion beam for deflecting ions entering the lens structure. In one embodiment of the lens structure, ions first encounter a first electrode for decelerating ions and then encounter a second electrode for accelerating the ions. The combined action of these electrodes causes ions entering the lens structure to exit the lens structure with approximately the same exit trajectory regardless of the trajectory of the ions as they enter the lens structure. In an alternate construction, the lens structure includes a first electrode along the beam path for accelerating ions and a second electrode downstream from the first electrode for decelerating ions. This alternative embodiment also causes ions entering the lens structure to exit the lens structure with approximately the same exit trajectory regardless of the trajectory of the ions as they enter the lens structure.
These and other objects, advantages and features of the invention are described in greater detail in conjunction with drawings which are used to describe an exemplary embodiment of the invention.